From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Date: Wed, 15 Apr 2015 23:17:02 +0000 (-0700)
Subject: lib/vsprintf.c: eliminate some branches
X-Git-Tag: omap-for-v4.1/fixes-rc1~128^2~30
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=51be17dfff753e72872f096ce1e654734f2fec50;p=pandora-kernel.git

lib/vsprintf.c: eliminate some branches

Since FORMAT_TYPE_INT is simply 1 more than FORMAT_TYPE_UINT, and
similarly for BYTE/UBYTE, SHORT/USHORT, LONG/ULONG, we can eliminate a few
instructions by making SIGN have the value 1 instead of 2, and then use
arithmetic instead of branches for computing the right spec->type.  It's a
little hacky, but certainly in the same spirit as SMALL needing to have
the value 0x20.  For example for the spec->qualifier == 'l' case, gcc now
generates

     75e:       0f b6 53 01             movzbl 0x1(%rbx),%edx
     762:       83 e2 01                and    $0x1,%edx
     765:       83 c2 09                add    $0x9,%edx
     768:       88 13                   mov    %dl,(%rbx)

instead of

     763:       0f b6 53 01             movzbl 0x1(%rbx),%edx
     767:       83 e2 02                and    $0x2,%edx
     76a:       80 fa 01                cmp    $0x1,%dl
     76d:       19 d2                   sbb    %edx,%edx
     76f:       83 c2 0a                add    $0xa,%edx
     772:       88 13                   mov    %dl,(%rbx)

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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